One electrophotographic image forming apparatus known in the art (hereinafter referred to as a first conventional image forming apparatus) includes a plurality of photosensitive members on which electrostatic latent images are formed. One such image forming apparatus known in the art includes four process cartridges and an image-forming unit to support the process cartridges. The process cartridges are provided for each of four colors used in the image forming apparatus and each include a photosensitive drum. In this image forming apparatus, a waste toner box serving to accommodate waste toner therein is provided in the image-forming unit at a leading end portion (i.e. downstream end portion) thereof in a direction in which the image-forming unit is pulled out of the apparatus. This conventional image forming apparatus also includes a belt-waste-toner conveying tube for conveying waste toner from a belt-cleaning device to the waste toner box.
Further, one electrophotographic image forming apparatus known in the art (hereinafter referred to as a second conventional image forming apparatus) is a printer including a device body that accommodates a sheet-feeding unit for supplying sheets of paper, and an image-forming unit for forming images on the sheets supplied by the sheet-feeding unit. The image-forming unit further includes a plurality of process cartridges arranged at intervals in a front-rear direction and respectively supporting photosensitive drums, and a transfer unit for transferring toner images formed on the photosensitive drums onto the sheets supplied from the sheet-feeding unit. One such color printer that has been proposed provides the sheet-feeding unit with conveying rollers for supplying the sheets to the image-forming unit, and provides the transfer unit with a conveying belt positioned in confrontation with the plurality of photosensitive drums for conveying the sheets. In this conventional color printer, the conveying rollers are disposed apart from and obliquely above and forward of the transfer unit so as to overlap the transfer unit when projected in the front-rear direction.
Further, one electrophotographic image forming apparatus known in the art (hereinafter referred to as a third conventional image forming apparatus) includes a plurality of photosensitive members on which electrostatic latent images are formed, and a plurality of developing units that supply developer to corresponding photosensitive members. One such image forming apparatus has a plurality of process cartridges corresponding to colors used in the image forming apparatus. Each process cartridge includes a photosensitive drum, a developing roller disposed on the upper rear side of the photosensitive drum, and a supply roller disposed on the upper rear side of the developing roller. The space in the process cartridge above the developing roller and the supply roller serves as a toner-accommodating chamber for accommodating toner.